TW202405855A - Method and system of image-forming multi-electron beams - Google Patents
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Abstract
Description
本發明係關於電子束系統。This invention relates to electron beam systems.
半導體製造工業之演進對良率管理及特定言之度量衡及檢測系統提出愈來愈高的要求。臨界尺寸不斷縮小，但工業需要減少用於達成高良率、高價值生產之時間。最小化從偵測到一良率問題至解決該問題之總時間判定一半導體製造商之投資回報率。The evolution of the semiconductor manufacturing industry has placed increasing demands on yield management and specific metrology and inspection systems. Critical dimensions continue to shrink, but industry needs to reduce the time it takes to achieve high-yield, high-value production. Minimizing the total time from detection of a yield issue to resolution determines a semiconductor manufacturer's return on investment.
製造諸如邏輯及記憶體裝置之半導體裝置通常包含使用大量製程來處理一半導體晶圓以形成半導體裝置之各種特徵及多個層級。例如，微影術係涉及將一圖案從一倍縮光罩轉印至配置於一半導體晶圓上之一光阻劑的一半導體製程。半導體製程之額外實例包含但不限於化學機械拋光(CMP)、蝕刻、沈積及離子植入。可將於一單一半導體晶圓上製造之多個半導體裝置之一配置分離成個別半導體裝置。Fabricating semiconductor devices, such as logic and memory devices, typically involves processing a semiconductor wafer using numerous processes to form various features and multiple levels of the semiconductor device. For example, lithography is a semiconductor process that involves transferring a pattern from a reticle to a photoresist disposed on a semiconductor wafer. Additional examples of semiconductor manufacturing processes include, but are not limited to, chemical mechanical polishing (CMP), etching, deposition, and ion implantation. One of a plurality of semiconductor devices fabricated on a single semiconductor wafer may be configured and separated into individual semiconductor devices.
在半導體製造期間之各個步驟使用檢測程序來偵測晶圓上之缺陷以促成製程中之較高良率及因此較高利潤。檢測始終為製造諸如積體電路(IC)之半導體裝置之一重要部分。然而，隨著半導體裝置之尺寸減小，檢測對於可接受半導體裝置之成功製造而言變得更為重要，此係因為較小缺陷可能引起裝置故障。例如，隨著半導體裝置之尺寸減小，尺寸減小之缺陷之偵測已變得有必要，此係因為甚至相對較小缺陷仍可能引起半導體裝置中之非所要像差。Inspection procedures are used at various steps during semiconductor manufacturing to detect defects on wafers to promote higher yields in the process and therefore higher profits. Inspection has always been an important part of manufacturing semiconductor devices such as integrated circuits (ICs). However, as the size of semiconductor devices decreases, inspection becomes more important to the successful fabrication of acceptable semiconductor devices because smaller defects can cause device failure. For example, as semiconductor devices have decreased in size, detection of defects of reduced size has become necessary because even relatively small defects may still cause undesirable aberrations in semiconductor devices.
然而，隨著設計規則縮小，半導體製程可更接近對程序之效能能力之限制進行操作。另外，隨著設計規則縮小，較小缺陷可能對裝置之電氣參數具有影響，此驅使更靈敏檢測。隨著設計規則縮小，藉由檢測偵測到之潛在良率相關缺陷之群體急劇增長，且藉由檢測偵測到之擾亂點缺陷之群體亦急劇增長。因此，可在晶圓上偵測到更多缺陷，且校正程序以消除全部缺陷可為困難的且昂貴的。判定缺陷之哪一者實際上對裝置之電氣參數及良率具有影響可容許程序控制方法專注於該等缺陷而在很大程度上忽略其他缺陷。此外，在較小設計規則下，程序誘發之故障在一些情況中趨於為系統性的。即，程序誘發之故障趨於在通常在設計內重複許多次之預定設計圖案處發生故障。消除空間系統性的電氣相關缺陷可對良率具有影響。However, as design rules shrink, semiconductor processes can operate closer to the limits of a program's performance capabilities. In addition, as design rules shrink, smaller defects may have an impact on the electrical parameters of the device, which drives more sensitive detection. As design rules shrink, the population of potentially yield-relevant defects detected by inspection grows dramatically, and the population of disruptive point defects detected by inspection also grows dramatically. As a result, more defects may be detected on the wafer, and correction procedures to eliminate all defects may be difficult and expensive. Determining which of the defects actually has an impact on the device's electrical parameters and yield can allow process control methods to focus on those defects while largely ignoring other defects. Furthermore, under smaller design rules, program-induced failures tend to be systemic in some cases. That is, program-induced failures tend to fail at predetermined design patterns that are often repeated many times within a design. Eliminating spatially systematic electrical-related defects can have an impact on yield.
一聚焦電子束系統通常用於產生或檢查物品之微結構，諸如用於積體電路之製造中之矽晶圓。電子束係用從一電子槍中之一發射器發射之電子形成，該電子束在其與晶圓相互作用以檢查微結構時充當一精細探針。一單一電子束先前用於晶圓檢測及檢視以檢查奈米臨界尺寸(CD)級別之成品或未完成IC組件。一單一電子束設備之處理量相當低。半導體製造商正在尋求較高處理量系統。A focused electron beam system is commonly used to create or inspect the microstructure of articles, such as silicon wafers used in the manufacture of integrated circuits. An electron beam is formed using electrons emitted from an emitter in an electron gun, which acts as a fine probe as it interacts with the wafer to examine the microstructure. A single electron beam was previously used for wafer inspection and inspection to inspect finished or unfinished IC components at the nanometer critical dimension (CD) level. The throughput of a single electron beam facility is quite low. Semiconductor manufacturers are seeking higher throughput systems.
一多電子束設備之處理量係由子射束之數目或總電子小射束之數目特性化。小射束數目愈大，則處理量將愈高。然而，增加小射束之數目被一成像投影光學器件阻止，該成像投影光學器件由包含一全域物鏡及維恩(Wien)過濾器之全域光學元件組成。在對更多電子小射束之需求增加以達到較高處理量之情況下，由於來自外小射束之離軸像差、源能量分散模糊、歸因於一維恩過濾器的存在之光學像散及歸因於在具有較多小射束之情況下的較高射束電流之強庫侖(Coulomb)相互作用影響，難以運用成像投影系統跨一較大視域(FOV)提供成像均勻性。The throughput of a multi-electron beam device is characterized by the number of sub-beams or the number of total electron beamlets. The larger the number of beamlets, the higher the throughput will be. However, increasing the number of beamlets is prevented by an imaging projection optics consisting of a global optical element including a global objective and a Wien filter. In situations where the need for more electron beamlets increases to achieve higher throughputs, optical aberrations due to off-axis aberrations from the outer beamlets, source energy dispersion blurring due to the presence of one-Wien filters, Astigmatism and strong Coulomb interaction effects due to higher beam currents with more beamlets make it difficult to provide imaging uniformity across a large field of view (FOV) using imaging projection systems.
先前電子束系統歸因於庫侖相互作用之影響而遭受低解析度。一多電子束系統之解析度在很大程度上受限於從中間影像平面(IIP)至晶圓之成像投影光學器件，其係接近晶圓之一射束交叉。小射束成像解析度主要由交叉周圍之庫侖相互作用效應閘控。Previous electron beam systems suffered from low resolution due to the effects of Coulomb interactions. The resolution of a multi-electron beam system is largely limited by the imaging projection optics from the intermediate image plane (IIP) to the wafer, which is a beam intersection close to the wafer. The resolution of small beam imaging is mainly controlled by the Coulomb interaction effect around the intersection.
先前電子束系統亦遭受歸因於一維恩過濾器之存在而具有源能量分散模糊及像散模糊之問題。為移除一多電子束設備中之小射束信號之間之串擾，一維恩過濾器藉由高維恩過濾器強度以一較大二次電子束(SEB)偏轉角將SEB與初級電子束(PEB)分離。此引起跨一大FOV之各小射束之較重源能量分散模糊及像散模糊。Previous electron beam systems have also suffered from source energy dispersion blur and astigmatism blur due to the presence of a Wien filter. To remove crosstalk between small beam signals in a multi-electron beam facility, a Wien filter separates the secondary electron beam (SEB) from the primary electron beam (SEB) at a larger deflection angle by using a high Wien filter strength. PEB) separation. This causes dispersion blur and astigmatic blur in the heavier source energy of each beamlet across a large FOV.
需要經改良系統及方法。Improved systems and methods are needed.
在一第一實施例中提供一種系統。該系統包含產生一電子束之一電子束源。該電子束源包含一尖端、一抑制電極及一引出電極。該系統進一步包含：一載物台，其經組態以將一晶圓固持於該電子束之一路徑中；一物鏡，其在該電子束之該路徑中；一維恩過濾器，其在該物鏡與該電子束源之間之該電子束之該路徑中；一轉移透鏡(transfer lens)，其在該維恩過濾器與該電子束源之間之該電子束之該路徑中；及一偵測陣列，其經組態以接收來自該載物台上之該晶圓之至少一個二次電子束。該轉移透鏡包含一極片及一轉移透鏡線圈。該物鏡包含：一上極片；一下極片；一物鏡線圈，其安置於該上極片上；一電荷控制板，其安置於該下極片上；一加速電極，其安置於該上極片與該下極片之間之該電子束之該路徑中；及一掃描器，其安置於該上極片上。In a first embodiment a system is provided. The system includes an electron beam source that generates an electron beam. The electron beam source includes a tip, a suppression electrode and an extraction electrode. The system further includes: a stage configured to hold a wafer in a path of the electron beam; an objective lens in the path of the electron beam; and a Wien filter in A transfer lens in the path of the electron beam between the objective lens and the electron beam source; and a transfer lens in the path of the electron beam between the Wien filter and the electron beam source; and A detection array configured to receive at least one secondary electron beam from the wafer on the stage. The transfer lens includes a pole piece and a transfer lens coil. The objective lens includes: an upper pole piece; a lower pole piece; an objective lens coil, which is arranged on the upper pole piece; a charge control plate, which is arranged on the lower pole piece; an accelerating electrode, which is arranged on the upper pole piece and in the path of the electron beam between the lower pole pieces; and a scanner positioned on the upper pole piece.
維恩過濾器可包含一靜電偏轉器及一磁偏轉器。The Wien filter may include an electrostatic deflector and a magnetic deflector.
該系統可進一步包含在電子束之路徑中之一準直透鏡及在該準直透鏡與電子束源之間的該電子束之該路徑中之一限束孔徑。The system may further include a collimating lens in the path of the electron beam and a beam limiting aperture in the path of the electron beam between the collimating lens and the electron beam source.
該系統可進一步包含：一孔徑陣列，其安置於電子束之路徑中；一微像散校正器(stigmator)陣列，其安置於該孔徑陣列與轉移透鏡之間之該電子束之該路徑中；一微偏轉器陣列，其安置於該微像散校正器陣列與該轉移透鏡之間之該電子束之該路徑中；及一微透鏡陣列，其安置於該微偏轉器陣列與該轉移透鏡之間之該電子束之該路徑中。該孔徑陣列將該電子束分離成複數個小射束。該複數個小射束包含至少100個該等小射束。該電子束可為在該孔徑陣列上游之一遠心射束。The system may further include: an aperture array disposed in the path of the electron beam; an array of micro-astigmators disposed in the path of the electron beam between the aperture array and the transfer lens; a micro-deflector array disposed in the path of the electron beam between the micro-astigmatism corrector array and the transfer lens; and a micro-lens array disposed between the micro-deflector array and the transfer lens in the path of the electron beam. The aperture array separates the electron beam into a plurality of beamlets. The plurality of beamlets includes at least 100 such beamlets. The electron beam may be a telecentric beam upstream of the aperture array.
在一例項中，電子束之路徑離開轉移透鏡係成一第一定向且離開維恩過濾器係成不同於該第一定向之一第二定向，使得該第一定向與該第二定向成一非平行角度。In one example, the path of the electron beam leaves the transfer lens in a first orientation and exits the Wien filter in a second orientation different from the first orientation, such that the first orientation is consistent with the second orientation. into a non-parallel angle.
該系統可包含在維恩過濾器與轉移透鏡之間的電子束之路徑中之一第二維恩過濾器。該第二維恩過濾器可包含一第二靜電偏轉器及一第二磁偏轉器。The system may include a second Wien filter in the path of the electron beam between the Wien filter and the transfer lens. The second Wien filter may include a second electrostatic deflector and a second magnetic deflector.
在一第二實施例中提供一種方法。該方法包含引導複數個小射束通過在一電子束源下游之一轉移透鏡，藉此聚焦電子束。引導該等小射束通過在該轉移透鏡下游之一維恩過濾器，藉此將一或多個二次電子束與該等小射束分離。引導該等小射束通過一物鏡之一上極片。該物鏡係在該維恩過濾器下游。引導該等小射束通過在該上極片下游之一加速電極。引導該等小射束通過安置於該物鏡之一下極片中之一電荷控制板。該電荷控制板係安置於該物鏡之與該上極片相對之一側上。引導該等小射束於一晶圓處。在一偵測陣列處接收來自該晶圓之至少一個二次電子束。A method is provided in a second embodiment. The method includes directing a plurality of beamlets through a transfer lens downstream of an electron beam source, thereby focusing the electron beam. The beamlets are directed through a Wien filter downstream of the transfer lens, thereby separating one or more secondary electron beams from the beamlets. The beamlets are directed through an upper pole piece of an objective lens. The objective is downstream of the Wien filter. The beamlets are directed through an accelerating electrode downstream of the upper pole piece. The beamlets are directed through a charge control plate disposed in a lower pole piece of the objective. The charge control plate is disposed on the side of the objective lens opposite to the upper pole piece. The beamlets are directed at a wafer. Receive at least one secondary electron beam from the wafer at a detection array.
複數個小射束可包含至少100個小射束。The plurality of beamlets may include at least 100 beamlets.
該方法可進一步包含使用電子束源產生一電子束及將該電子束轉換成複數個小射束。The method may further include generating an electron beam using an electron beam source and converting the electron beam into a plurality of beamlets.
該方法可進一步包含引導電子束通過一準直透鏡及安置於電子束源與轉移透鏡之間的電子束之一路徑中之一限束孔徑。The method may further include directing the electron beam through a collimating lens and a beam limiting aperture disposed in a path of the electron beam between the electron beam source and the transfer lens.
該方法可進一步包含運用安置於上極片上之一掃描器來掃描小射束。The method may further include scanning the beamlet using a scanner disposed on the upper pole piece.
維恩過濾器可包含一靜電偏轉器及一磁偏轉器。The Wien filter may include an electrostatic deflector and a magnetic deflector.
該方法可進一步包含：使用一孔徑陣列將一電子束分離成小射束；引導該等小射束通過安置於該孔徑陣列與轉移透鏡之間的該等小射束之路徑中之一微像散校正器陣列；引導該等小射束通過安置於該微像散校正器陣列與該轉移透鏡之間的該等小射束之該路徑中之一微偏轉器陣列；及引導該等小射束通過安置於該微偏轉器陣列與該轉移透鏡之間的該等小射束之該路徑中之一微透鏡陣列。該孔徑陣列係安置於電子束源與該轉移透鏡之間之該電子束之一路徑中。該複數個小射束可包含至少100個該等小射束。該電子束可為在該孔徑陣列上游之一遠心射束。The method may further include: splitting an electron beam into beamlets using an aperture array; directing the beamlets through a micro-image in the path of the beamlets disposed between the aperture array and the transfer lens an astigmatism corrector array; guiding the beamlets through a micro-deflector array in the path of the beamlets disposed between the micro-astigmatism corrector array and the transfer lens; and guiding the beamlets The beam passes through a microlens array in the path of the beamlets disposed between the microdeflector array and the transfer lens. The aperture array is disposed in a path of the electron beam between the electron beam source and the transfer lens. The plurality of beamlets may include at least 100 such beamlets. The electron beam may be a telecentric beam upstream of the aperture array.
該方法可進一步包含使用維恩過濾器改變小射束之一方向，使得該等小射束離開該維恩過濾器係按相對於其等進入該維恩過濾器的定向之一角度引導。The method may further comprise using a Wien filter to change a direction of the beamlets such that the beamlets exiting the Wien filter are directed at an angle relative to their orientation entering the Wien filter.
該方法可進一步包含引導小射束通過在維恩過濾器與轉移透鏡之間的小射束之一路徑中之一第二維恩過濾器。The method may further include directing the beamlet through a second Wien filter in one of the beamlet's paths between the Wien filter and the transfer lens.
加速電極可經組態以改變小射束之解析度。The accelerating electrodes can be configured to vary the resolution of the beamlets.
維恩過濾器可經組態以同時調整小射束之分散及像散。Wien filters can be configured to simultaneously adjust for beamlet dispersion and astigmatism.
儘管將依據特定實施例描述所主張標的物，然其他實施例(包含未提供本文中所闡述之全部優點及特徵之實施例)亦在本發明之範疇內。可作出各種結構、邏輯、程序步驟及電子改變而不脫離本發明之範疇。因此，僅藉由參考隨附發明申請專利範圍來定義本發明之範疇。Although the claimed subject matter will be described in terms of specific embodiments, other embodiments, including embodiments that do not provide all of the advantages and features set forth herein, are within the scope of the invention. Various structural, logical, procedural and electronic changes may be made without departing from the scope of the invention. Accordingly, the scope of the present invention is defined solely by reference to the accompanying patent claims.
本文中揭示形成數百個小射束之一多電子束系統。一轉移透鏡(TL)場將小射束聚焦至一最佳光學放大率。一能量加速增壓器場降低庫侖相互作用效應且改良小射束之解析度。可使用一電子能量延遲(減速)及基板充電場來獲得所要晶圓充電、引出場及著陸能量。一磁性物鏡場可以最小化光學像差使多電子束在一晶圓處成像。具有靜電及磁偏轉場之一維恩過濾器可將一或多個二次電子束(SEB)與一或多個初級電子束分離且可同時校正全部小射束之源能量分散模糊。維恩過濾器可包含一靜電(或磁)像散校正器場以同時校正小射束像散。轉移透鏡可選擇一光學放大率且加速電極可降低庫侖相互作用。在一實施例中，可歸因於一維恩過濾器之存在而校正小射束之源能量分散模糊。在另一實施例中，可歸因於一維恩過濾器之存在而校正小射束之像散模糊。在又一實施例中，可補償兩個維恩過濾器之間之源能量分散，使得移除小射束之全部能量分散模糊且同時將二次電子束偏轉至側偵測陣列。This article reveals a multi-electron beam system that forms one of hundreds of small beams. A transfer lens (TL) field focuses the beamlet to an optimal optical magnification. An energy accelerating booster field reduces Coulomb interaction effects and improves beamlet resolution. An electron energy delay (deceleration) and substrate charging field can be used to obtain the desired wafer charging, extraction field and landing energies. A magnetic objective field minimizes optical aberrations and allows multiple electron beams to be imaged on a wafer. A Wien filter with electrostatic and magnetic deflection fields can separate one or more secondary electron beams (SEB) from one or more primary electron beams and can correct the source energy dispersion blur of all beamlets simultaneously. The Wien filter may contain an electrostatic (or magnetic) astigmatism corrector field to simultaneously correct beamlet astigmatism. The transfer lens selects an optical magnification and the accelerating electrode reduces Coulomb interactions. In one embodiment, the source energy dispersion blur of the beamlet may be corrected due to the presence of a Wien filter. In another embodiment, the astigmatic blur of the beamlet may be corrected due to the presence of a Wien filter. In yet another embodiment, the source energy dispersion between the two Wien filters can be compensated such that all energy dispersion blur of the beamlet is removed while simultaneously deflecting the secondary electron beam to the side detection array.
圖1展示一多電子束設備之一實施例之光學器件。其包含電子槍(「槍」)、準直透鏡(「CL」)、多電子束產生(「MBC」)及投影成像(「投影」)之四個光學模組。Figure 1 shows the optics of one embodiment of a multi-electron beam apparatus. It includes four optical modules: electron gun ("gun"), collimating lens ("CL"), multiple electron beam generation ("MBC") and projection imaging ("projection").
如圖1中所展示，系統100包含產生一電子束113之一電子束源。電子束源可包含一尖端101。電子束源亦可包含一抑制電極及引出電極。電子束源可為從一發射器尖端發射電子之一熱場發射(TFE)或冷場發射(CFE)源。電子係由一槍透鏡(GL) 102聚焦成一大尺寸電子束113。高電流電子束113係由準直透鏡126準直成一遠心射束以照明一孔徑陣列103 (AA)。孔徑陣列103亦可被稱為一微孔徑陣列。諸如一陽極之一額外電子能量加速元件可搭配電子束源使用。As shown in FIG. 1 , system 100 includes an electron beam source that generates an electron beam 113 . The electron beam source may include a tip 101 . The electron beam source may also include a suppression electrode and extraction electrode. The electron beam source may be a thermal field emission (TFE) or cold field emission (CFE) source that emits electrons from an emitter tip. The electrons are focused by a gun lens (GL) 102 into a large size electron beam 113. The high current electron beam 113 is collimated by collimating lens 126 into a telecentric beam to illuminate an aperture array 103 (AA). Aperture array 103 may also be referred to as a microaperture array. An additional electron energy accelerating element, such as an anode, may be used with the electron beam source.
在槍透鏡102之後之限束孔徑(BLA) 125可選擇照明孔徑陣列103之總射束電流，孔徑陣列103將電子束113分離成小射束114。孔徑陣列103係用於選擇各單一小射束114之射束電流。對於各小射束114，在孔徑陣列103中存在一個孔。孔可為圓形、六邊形或其他形狀。為簡單起見在圖1中繪示三個小射束114，但其他數目係可能的。例如，可存在至少100個小射束114 (例如，大於300個)。在孔徑陣列103下游，一微透鏡陣列(MLA) 106將各小射束114聚焦至一中間影像平面(IIP)上。微透鏡陣列106中之各微透鏡可為一磁透鏡或靜電透鏡。一磁性微透鏡可為由線圈激勵或永磁體供電之若干磁極片。一靜電微透鏡可為一靜電單透鏡或一靜電加速/減速單電位透鏡。A beam limiting aperture (BLA) 125 after the gun lens 102 selects the total beam current of the illumination aperture array 103 that separates the electron beam 113 into small beams 114. Aperture array 103 is used to select the beam current for each individual beamlet 114 . For each beamlet 114, there is one hole in the aperture array 103. The holes can be round, hexagonal or other shapes. Three beamlets 114 are shown in Figure 1 for simplicity, but other numbers are possible. For example, there may be at least 100 beamlets 114 (eg, greater than 300). Downstream of aperture array 103, a microlens array (MLA) 106 focuses each beamlet 114 onto an intermediate image plane (IIP). Each microlens in the microlens array 106 can be a magnetic lens or an electrostatic lens. A magnetic microlens can be a plurality of pole pieces powered by coils or permanent magnets. An electrostatic microlens can be an electrostatic single lens or an electrostatic acceleration/deceleration single potential lens.
系統100包含在電子束113之路徑中之一準直透鏡126。準直透鏡126可為一靜電透鏡或一磁透鏡，其用以在照明MBC模組之前將來自槍之發散電子束聚焦成一遠心射束。準直透鏡126可減少外電子小射束之槍球面像差，此可輔助增加小射束數目以獲得較高處理量。限束孔徑125係在準直透鏡126與電子束源之間之電子束113之路徑中。System 100 includes a collimating lens 126 in the path of electron beam 113 . The collimating lens 126 may be an electrostatic lens or a magnetic lens that is used to focus the diverging electron beam from the gun into a telecentric beam before illuminating the MBC module. The collimating lens 126 can reduce the gun spherical aberration of the external electron beamlets, which can assist in increasing the number of beamlets to achieve higher throughput. The beam limiting aperture 125 is in the path of the electron beam 113 between the collimating lens 126 and the electron beam source.
一微像散校正器陣列104 (MSA)係安置於孔徑陣列103與轉移透鏡112之間之電子束113之路徑中且可校正各小射束114之像散。一微偏轉器陣列105 (MDA)係安置於微像散校正器陣列104與轉移透鏡112之間之電子束113之路徑中。微偏轉器陣列105可校正各小射束114之失真及/或以一給定子FOV在晶圓107上方掃描各小射束114。一微透鏡陣列106 (MLA)係安置於微偏轉器陣列105與轉移透鏡112之間之電子束113之路徑中。術語「微」可指代組件之大小，但亦可指示此等組件係搭配小射束114使用。小射束114小於電子束113。A micro-astigmatism corrector array 104 (MSA) is disposed in the path of the electron beam 113 between the aperture array 103 and the transfer lens 112 and corrects the astigmatism of each beamlet 114. A micro-deflector array 105 (MDA) is disposed in the path of the electron beam 113 between the micro-astigmatism corrector array 104 and the transfer lens 112 . Micro-deflector array 105 may correct the distortion of each beamlet 114 and/or scan each beamlet 114 over wafer 107 with a given sub-FOV. A microlens array 106 (MLA) is disposed in the path of the electron beam 113 between the microdeflector array 105 and the transfer lens 112 . The term "micro" may refer to the size of the components, but may also indicate that these components are used with small beams 114. Beamlet 114 is smaller than electron beam 113 .
一載物台108經組態以將一晶圓107固持於電子束113之小射束114之一路徑中。一物鏡109及一維恩過濾器110係在載物台108上游。A stage 108 is configured to hold a wafer 107 in a path of beamlet 114 of electron beam 113 . An objective lens 109 and a Wien filter 110 are located upstream of the stage 108 .
電子源從尖端101發射電子且接著電子由一槍透鏡102加速且聚焦成一大尺寸之電子束113。具有高射束電流之電子束113係由準直透鏡126準直成一遠心射束以照明孔徑陣列103。在給定源亮度或角強度之情況下，電子束113係由圖1中之尖端發射角α特性化。在槍透鏡102之後之限束孔徑125係用於選擇照明孔徑陣列103之總射束電流。孔徑陣列103係用於選擇各單一小射束114之射束電流。在孔徑陣列103、微像散校正器陣列104及微偏轉器陣列105之後，微透鏡陣列106將各小射束114聚焦至中間影像平面上。中間影像平面係下柱中之投影成像光學器件之物件平面。An electron source emits electrons from tip 101 and the electrons are then accelerated and focused by a gun lens 102 into a large size electron beam 113. The electron beam 113 with high beam current is collimated by collimating lens 126 into a telecentric beam to illuminate aperture array 103. At a given source brightness or angular intensity, the electron beam 113 is characterized by the tip emission angle α in FIG. 1 . The beam limiting aperture 125 after the gun lens 102 is used to select the total beam current of the illumination aperture array 103. Aperture array 103 is used to select the beam current for each individual beamlet 114 . Following the aperture array 103, the micro-astigmatism corrector array 104 and the micro-deflector array 105, the micro-lens array 106 focuses each beamlet 114 onto the intermediate image plane. The intermediate image plane is the object plane of the projection imaging optics in the lower column.
在轉移透鏡112與物鏡109之間存在一射束交叉(xo)。中間影像平面處由上柱形成之小射束114係由轉移透鏡112及物鏡109以一所要放大率投影於晶圓(WF) 107上。放大率可經組態以最小化晶圓處之各小射束之所有射束模糊。最佳放大率被給定為D i/D o，其中D i及D o分別為晶圓平面(影像平面)及中間影像平面(物件平面)中之多電子束(MB) FOV。轉移透鏡112可選擇射束交叉(xo)之一所要位置(或交叉角θ)，在該位置處，各小射束114之總光斑大小係最小的，同時平衡電子之間之軸向像差、離軸像差及庫侖相互作用。 There is a beam intersection (xo) between transfer lens 112 and objective lens 109 . The beamlet 114 formed by the upper pillar at the intermediate image plane is projected onto the wafer (WF) 107 by the transfer lens 112 and the objective lens 109 at a desired magnification. The magnification can be configured to minimize overall beam blur for each beamlet at the wafer. The optimal magnification is given as Di / Do , where Di and Do are the multi-beam (MB) FOV in the wafer plane (image plane) and the intermediate image plane (object plane), respectively. The transfer lens 112 can select a desired position (or intersection angle θ) of the beam intersections (xo) at which the total spot size of each beamlet 114 is minimized while balancing axial aberrations between electrons , off-axis aberration and Coulomb interaction.
為檢測及檢視一晶圓，歸因於各初級小射束114電子之轟擊而從晶圓107發射之二次電子(SE)及/或反向散射電子(BSE)可從光軸分離且由維恩過濾器110偏轉朝向偵測陣列111。To inspect and inspect a wafer, secondary electrons (SE) and/or backscattered electrons (BSE) emitted from the wafer 107 due to the bombardment of electrons from each primary beamlet 114 can be separated from the optical axis and produced by The Wien filter 110 is deflected towards the detection array 111 .
如圖2中所展示，物鏡109係在電子束113之小射束114之路徑中。物鏡109包含一上極片115及一下極片116。一物鏡線圈117係安置於上極片115上。一電荷控制板118係安置於下極片116上。一加速電極119係安置於上極片115與下極片116之間之電子束113之路徑中。一掃描器120係安置於上極片115上。掃描器120可以相同方式(例如，光柵掃描)及相同掃描FOV同時掃描所有小射束114。掃描FOV大小係用晶圓107上之小射束節距給出。As shown in FIG. 2 , objective lens 109 is in the path of beamlet 114 of electron beam 113 . The objective lens 109 includes an upper pole piece 115 and a lower pole piece 116 . An objective lens coil 117 is arranged on the upper pole piece 115 . A charge control board 118 is disposed on the lower pole piece 116 . An accelerating electrode 119 is disposed in the path of the electron beam 113 between the upper pole piece 115 and the lower pole piece 116 . A scanner 120 is placed on the upper pole piece 115 . Scanner 120 may scan all beamlets 114 simultaneously in the same manner (eg, raster scan) and with the same scan FOV. The scan FOV size is given by the small beam pitch on the wafer 107.
維恩過濾器110係在物鏡109與電子束源之間的電子束113之小射束114之路徑中。在一實施例中，維恩過濾器110包含一靜電偏轉器121及一磁偏轉器122。A Wien filter 110 is placed in the path of the beamlet 114 of the electron beam 113 between the objective 109 and the electron beam source. In one embodiment, the Wien filter 110 includes an electrostatic deflector 121 and a magnetic deflector 122 .
維恩過濾器110可在操作期間被移除或未啟動。此對於多電子束微影或運用一環形偵測陣列(例如，具有與初級射束光軸相同之中心偵測器軸)之多電子束檢視及檢測可為有益的。微影術係在晶圓光阻劑上之一直接書寫而無需收集二次電子或無需將初級電子(PE)與二次電子分離。若使用一環形偵測陣列，則各SE小射束直接命中一固定子偵測器而無需改變方向(偏轉)。因此，此等應用可能無需一維恩過濾器。例如，對於一較簡單應用，射束能量及著陸能量皆為固定的以用於一種特殊用途，且SE軌跡係固定的。若使用條件改變，則SE軌跡亦改變。在此情況中，固定環形偵測陣列可能不足以滿足所有應用。Wien filter 110 may be removed or not activated during operation. This can be beneficial for multi-electron beam lithography or multi-electron beam inspection and inspection using an annular detection array (eg, with a central detector axis that is the same as the primary beam optical axis). Lithography writes directly on the wafer photoresist without collecting secondary electrons or separating primary electrons (PE) from secondary electrons. If an annular detection array is used, each SE beamlet directly hits a stationary detector without changing direction (deflection). Therefore, a 1-Wien filter may not be required for such applications. For example, for a simpler application, the beam energy and landing energy are both fixed for a particular application, and the SE trajectory is fixed. If the usage conditions change, the SE trajectory also changes. In this case, a fixed ring detection array may not be sufficient for all applications.
一轉移透鏡112 (TL)係在維恩過濾器110與電子束源之間的電子束113之小射束114之路徑中。轉移透鏡112包含一極片123及一轉移透鏡線圈124。轉移透鏡112可為用於運用經整形射束或多電子束改良離軸光學效能之一磁透鏡。A transfer lens 112 (TL) is in the path of the beamlets 114 of the electron beam 113 between the Wien filter 110 and the electron beam source. The transfer lens 112 includes a pole piece 123 and a transfer lens coil 124 . Transfer lens 112 may be a magnetic lens used to improve off-axis optical performance using shaped beams or multiple electron beams.
物鏡109可包含一靜電區段及一磁區段。物鏡109之靜電區段可包含接地電極、具有電壓Va之加速電極119、電荷控制板118及載物台108。此等組件之一或多者可用於對晶圓107進行充電且將電子從射束能量延遲(減速)至晶圓107上之著陸能量。例如，若一電子束在柱中為30 keV，則針對1 keV之一電子束著陸能量，可在-29 kV加偏壓於晶圓107。1 keV可用於電子束檢測及檢視，但其他值係可能的。為運用晶圓表面上之一引出場對晶圓107進行充電，應根據應用要求加偏壓於電荷控制板118。物鏡109之磁區段可包含上極片115、下極片116及線圈。上極片115及下極片116可由磁性材料製成。上極片115可連接至接地電極，如維恩過濾器屏蔽件或掃描器屏蔽件。下極片116可連接至電荷控制板118電極。下極片116與上極片115之間之外間隙可用絕緣體材料密封。Objective lens 109 may include an electrostatic segment and a magnetic segment. The electrostatic section of the objective lens 109 may include a ground electrode, an accelerating electrode 119 with a voltage Va, a charge control plate 118 and a stage 108. One or more of these components may be used to charge wafer 107 and delay (slow down) electrons from beam energy to landing energy on wafer 107 . For example, if an electron beam is 30 keV in the column, then the wafer 107 can be biased at -29 kV for an electron beam landing energy of 1 keV. 1 keV can be used for electron beam detection and inspection, but other values It is possible. To charge wafer 107 using one of the extraction fields on the wafer surface, charge control plate 118 should be biased according to the application requirements. The magnetic section of the objective 109 may include an upper pole piece 115, a lower pole piece 116 and a coil. The upper pole piece 115 and the lower pole piece 116 can be made of magnetic materials. The upper pole piece 115 may be connected to a ground electrode, such as a Wien filter shield or scanner shield. The lower pole piece 116 may be connected to the charge control plate 118 electrode. The outer gap between the lower pole piece 116 and the upper pole piece 115 can be sealed with an insulator material.
一偵測陣列111 (DA)經組態以接收來自載物台108上之晶圓107之二次電子束。可使用來自偵測陣列111之信號來產生量測值或影像。偵測陣列111可與用於影像產生、檢測、度量衡或其他功能之一處理器電子通信。A detection array 111 (DA) is configured to receive the secondary electron beam from wafer 107 on stage 108 . Signals from the detection array 111 may be used to generate measurements or images. The detection array 111 may be in electronic communication with a processor for image generation, detection, metrology, or other functions.
圖1中之多電子束交叉(xo)係配置於加速電極119周圍以降低庫侖相互作用(CI)，此係因為CI誘發之光學模糊可能主導晶圓107處之各小射束114之解析度。可能主要在交叉處產生庫侖相互作用。將交叉配置於加速電極119周圍可使電子加速，此可降低庫侖效應。The multiple electron beam intersections (xo) in FIG. 1 are arranged around the accelerating electrode 119 to reduce Coulomb interaction (CI) because CI-induced optical blur may dominate the resolution of each beamlet 114 at the wafer 107 . Coulomb interactions may occur mainly at the intersections. Arranging the crosses around the accelerating electrode 119 can accelerate electrons, which can reduce the Coulomb effect.
圖2中之掃描器120可同時在一FOV內掃描所有電子小射束114。亦可運用圖1中之微偏轉器陣列105各別地掃描各小射束，其中可獨立地控制各微偏轉器。The scanner 120 in Figure 2 can scan all electron beamlets 114 within a FOV simultaneously. The micro-deflector array 105 in Figure 1 can also be used to scan each beamlet individually, where each micro-deflector can be controlled independently.
維恩過濾器110可包含具有正交靜電場(E場)及磁場(B場)之一靜電偏轉器及一磁偏轉器。此係由靜電偶極121及磁偶極122展示。圖3展示包含一個八極靜電偏轉器及一個八極磁偏轉器之一維恩過濾器之構造。使用磁偏轉場作為一實例，圖3展示八極磁偏轉器(MD)之橫截面視圖。八個磁極片係以一旋轉對稱方式配置為一個八極偏轉器，且相同數目個線圈匝係纏繞在各極片周圍。極片如圖3中展示般被屏蔽。運用通過線圈之電流之適合設定，一較大中心區域中之磁偏轉場之分佈可能相當均勻，以最小化數百個小射束中之外射束之彗形像差模糊。例如，針對y軸方向上之一均勻B場，可將線圈電流施加為Iy=1個單位，Ix=0個單位，及縮放因數a=1/√2。在另一實例中，針對x軸方向上之一均勻B場，可將線圈電流施加為Ix=1個單位，Iy=0個單位，及a=1/√2。Wien filter 110 may include an electrostatic deflector and a magnetic deflector with orthogonal electrostatic fields (E field) and magnetic fields (B field). This is demonstrated by the electrostatic dipole 121 and the magnetic dipole 122 . Figure 3 shows the structure of a Wien filter including an eight-pole electrostatic deflector and an eight-pole magnetic deflector. Using a magnetic deflection field as an example, Figure 3 shows a cross-sectional view of an eight-pole magnetic deflector (MD). The eight magnetic pole pieces are configured in a rotationally symmetrical manner as an eight-pole deflector, and the same number of coil turns are wound around each pole piece. The pole pieces are shielded as shown in Figure 3. With appropriate settings of the current through the coil, the distribution of the magnetic deflection field in a large central area can be sufficiently uniform to minimize coma blurring of the outer beams among hundreds of small beams. For example, for a uniform B field in the y-axis direction, the coil current can be applied as Iy=1 unit, Ix=0 units, and the scaling factor a=1/√2. In another example, for a uniform B field in the x-axis direction, the coil current can be applied as Ix=1 unit, Iy=0 units, and a=1/√2.
圖4中展示一個八極靜電偏轉器(ED)，其係從圖3之虛線區域截取。若設定偏轉電壓為Vx=1個單位，Vy=0個單位及縮放因數a=1/√2，則運用一較大中心區域中之相當均勻場分佈來產生x軸方向上之靜電偏轉場，如在直線等電位線上可見。Figure 4 shows an eight-pole electrostatic deflector (ED) taken from the dashed area of Figure 3. If the deflection voltage is set to Vx=1 unit, Vy=0 unit and the scaling factor a=1/√2, then a fairly uniform field distribution in a large central area is used to generate the electrostatic deflection field in the x-axis direction, As seen on straight equipotential lines.
進行電腦模擬以證實晶圓處之數百個電子小射束成像，如圖5中所展示。圖5中之實例係針對具有六邊形分佈之331個電子小射束，但其他數目個小射束或分佈係可能的。晶圓107處之多電子束FOV (即，圖1中之D i)被定義為最遠隅角射束至最遠隅角射束，若從IIP至晶圓之光學縮小率(demagnification)係8X，則其可為圖1中之晶圓107處從大約200微米至300微米之D i或IIP處從大約1600微米至2400微米之D o。 Computer simulations were performed to demonstrate imaging of hundreds of electron beamlets at the wafer, as shown in Figure 5. The example in Figure 5 is for 331 electron beamlets with a hexagonal distribution, but other numbers of beamlets or distributions are possible. The multi-electron beam FOV at wafer 107 (i.e., D i in Figure 1 ) is defined as the farthest corner beam to the farthest corner beam, if the optical demagnification from IIP to the wafer is 8X, then it can be D i from about 200 microns to 300 microns at wafer 107 in FIG. 1 or D o from about 1600 microns to 2400 microns at IIP.
進一步進行電腦模擬以證實光斑大小對射束電流關係，如圖6中所展示。總射束電流係所有小射束(例如，圖5中之331個射束)電流之加總，且光斑大小反映包含考量所有光學模糊(例如，歸因於透鏡像差及歸因於電子之間之庫侖相互作用的模糊)之光學效能(解析度)。在模擬中，加速電壓Va分別經施加具有0 kV、25 kV、50 kV及100 kV。對於各加速電壓Va，物鏡109之磁激勵(線圈電流)係用於將射束聚焦於晶圓107上。交叉(xo)係設定在加速電極119 (Va)周圍以用於將交叉周圍之射束能量提高至(BE+Va)，其中BE係在電子被加速之前柱中之射束能量。基於圖6，增壓器上之加速電壓Va可幫助改良多電子束解析度。Further computer simulations were performed to confirm the spot size versus beam current relationship, as shown in Figure 6. The total beam current is the sum of the currents of all small beams (e.g., 331 beams in Figure 5), and the spot size reflection includes accounting for all optical blur (e.g., due to lens aberrations and due to electrons). The optical performance (resolution) of the Coulomb interaction between the In the simulation, the accelerating voltage Va was applied with 0 kV, 25 kV, 50 kV and 100 kV respectively. For each acceleration voltage Va, the magnetic excitation (coil current) of the objective 109 is used to focus the beam on the wafer 107 . The intersection (xo) is set around the accelerating electrode 119 (Va) to increase the beam energy around the intersection to (BE+Va), where BE is the beam energy in the column before the electrons are accelerated. Based on Figure 6, the acceleration voltage Va on the booster can help improve multi-electron beam resolution.
儘管圖5展示晶圓107處之電子束光斑之分佈，然其可進一步用於繪示圖1及圖2中之光學器件之x-y平面中之一些性質。Although FIG. 5 shows the distribution of the electron beam spot at wafer 107, it can be further used to illustrate some properties in the x-y plane of the optical device in FIGS. 1 and 2.
圖5展示圖1中之孔徑陣列103。孔徑陣列103之孔可為六邊形分佈的，此係因為六邊形在光學中接近旋轉對稱。其他形狀係可能的。孔徑陣列103中之各孔之大小係用於選擇一小射束之電子電流。孔徑陣列103中之孔之數目係小射束之數目。FIG. 5 shows the aperture array 103 of FIG. 1 . The holes of the aperture array 103 may be hexagonally distributed because hexagons are close to rotational symmetry in optics. Other shape systems are possible. The size of each hole in aperture array 103 is used to select a small beam of electron current. The number of holes in aperture array 103 is the number of beamlets.
可按方程式(1)來縮放圖1中之總MB (多電子束)數(MB tot)。 The total MB (multiple electron beam) number (MB tot ) in Figure 1 can be scaled according to equation (1).
在方程式(1)中，M x係圖5中之x軸上之所有小射束之數目。例如，在圖5中之六邊形分佈之小射束之五個環內，x軸上之所有小射束之數目係M x=11，而給出總小射束之數目MB tot=91。在10個環內，M x=21，且MB tot=331。 In equation (1), M x is the number of all beamlets on the x-axis in Figure 5. For example, within the five rings of hexagonally distributed beamlets in Figure 5, the number of all beamlets on the x-axis is M x =11, giving the total number of beamlets MB tot =91 . Within 10 rings, M x =21, and MB tot =331.
圖5亦可展示圖1中之微像散校正器陣列104中之各微像散校正器、微偏轉器陣列105中之各微偏轉器及微透鏡陣列106中之各微透鏡的位置及大小。圖5亦可展示圖1及圖2中之中間影像平面，其中多電子束經成像具有呈六邊形分佈之一中間光斑大小陣列。Figure 5 can also show the position and size of each micro-astigmatism corrector in the micro-astigmatism corrector array 104, each micro-deflector in the micro-deflector array 105, and each micro-lens in the micro-lens array 106 in Figure 1 . Figure 5 also shows the intermediate image plane in Figures 1 and 2, in which multiple electron beams are imaged with an array of intermediate spot sizes in a hexagonal distribution.
圖5亦展示圖1及圖2中之樣本(晶圓)平面，其中多電子束經成像具有呈六邊形分佈之一最終光斑大小陣列。從中間影像平面至晶圓平面，多電子束FOV被縮小為1/M。M係從IIP至晶圓之一光學放大率。在圖1中，光學放大率係M=D i/D o，其中D i及D o分別被稱為投影光學器件之影像平面及物件平面中之FOV。D o=2xn=2np，其中n係六邊形環之數目且p係小射束之間之間距。 Figure 5 also shows the sample (wafer) plane in Figures 1 and 2 in which the multiple electron beams are imaged with a final spot size array in a hexagonal distribution. From the intermediate image plane to the wafer plane, the multi-beam FOV is reduced to 1/M. M is the optical magnification from IIP to wafer. In Figure 1, the optical magnification is M=D i /D o , where Di and Do are respectively called the FOV in the image plane and object plane of the projection optical device. D o =2xn=2np, where n is the number of hexagonal rings and p is the distance between beamlets.
運用圖5，用方程式(1)來計算總小射束且用環號(第n環，n=0,1,2,3,…)及極角來定址各小射束。例如，(第10環，60°)及(第10環，120°)分別定址成60°及120°之最遠隅角小射束。Using Figure 5, use equation (1) to calculate the total beamlets and address each beamlet using the ring number (nth ring, n=0,1,2,3,…) and polar angle. For example, (10th ring, 60°) and (10th ring, 120°) are addressed to the farthest corner angle beamlets of 60° and 120° respectively.
在期望具有更多電子小射束之更高處理量之情況下，圖1及圖2中之二次電子束可與光軸分離且經偏轉朝向一側偵測陣列111以用於減少二次電子束之間之串擾。圖1及圖2中之維恩過濾器可實現此分離。然而，此可引入晶圓107處之小射束之能量分散模糊，此係因為從電子源發射之所有電子具有一能量發散(例如，對於一TFE源，大約1 eV)。In situations where higher throughput with more electron beamlets is desired, the secondary electron beams in Figures 1 and 2 can be separated from the optical axis and deflected towards one side of the detection array 111 for reducing secondary electron beams. Crosstalk between electron beams. The Wien filter in Figures 1 and 2 can achieve this separation. However, this can introduce ambiguity in the energy dispersion of the beamlet at wafer 107 because all electrons emitted from the electron source have an energy dispersion (eg, about 1 eV for a TFE source).
圖1及圖2中之光學系統之電腦模擬展示晶圓處之小射束光斑之電子在相同方向上擴展及分佈，如圖7中所展示，此係因為電子之能量分散角僅分佈在靜電力與磁力之間之維恩過濾器平衡之方向(例如，x軸或y軸方向)上。即使在電子經歷磁性物鏡109之聚焦時電子之旋轉之情況下，電子仍保持能量分散分佈之相同方向。圖7展示中心(第0環)及第10環處分別具有0°、60°、120°、180°、240°及300°的典型小射束之七個源能量分散模糊。Computer simulations of the optical systems in Figures 1 and 2 show that the electrons in the small beam spot at the wafer are expanded and distributed in the same direction, as shown in Figure 7. This is because the energy dispersion angle of the electrons is only distributed in the electrostatic In the direction of the Wien filter balance between force and magnetism (for example, the x-axis or y-axis direction). Even if the electrons rotate when they undergo focusing by the magnetic objective lens 109, the electrons still maintain the same direction of the energy dispersion distribution. Figure 7 shows seven source energy dispersion blurs of typical beamlets with 0°, 60°, 120°, 180°, 240° and 300° at the center (0th ring) and 10th ring respectively.
可運用一全域傾斜光學柱來校正歸因於維恩過濾器110之存在之所有小射束之源能量分散模糊，如圖8中所展示，其中θ p係初級多電子束相對於維恩過濾器110之中心的柱傾斜角，且θ s係朝向偵測陣列111之二次電子束(SEB)角。電子束114之路徑離開轉移透鏡112係成一第一定向且離開維恩過濾器110係成不同於第一定向之一第二定向，使得第一定向與第二定向成一非平行角度。θ s係藉由維恩過濾器110之二次電子束偏轉角。若角度θ p及θ s符合特定條件，則可校正圖7中之全部能量分散模糊。針對多射束用途，二次電子角θ s可為大約10°至45°且可用方程式給出初級電子束角θ s。 A globally tilted optical column can be used to correct for source energy dispersion blur of all beamlets due to the presence of Wien filter 110, as shown in Figure 8, where θ p is the primary multi-electron beam relative to the Wien filter is the column tilt angle at the center of the detector 110, and θ s is the secondary electron beam (SEB) angle toward the detection array 111. The path of the electron beam 114 leaves the transfer lens 112 in a first orientation and leaves the Wien filter 110 in a second orientation that is different from the first orientation, such that the first orientation and the second orientation form a non-parallel angle. θ s is the deflection angle of the secondary electron beam by the Wien filter 110 . If the angles θ p and θ s meet specific conditions, all energy dispersion blur in Figure 7 can be corrected. For multi-beam applications, the secondary electron angle θ s can be from about 10° to 45° and the primary electron beam angle θ s can be given by an equation.
若圖8中之角度θ p及θ s符合方程式(2)中所定義之關係，則由一維恩過濾器110中之靜電及磁偏轉場產生之源能量分散模糊可彼此抵消。方程式(2)及(3)可用於平衡能量分散之校正。 If the angles θ p and θ s in FIG. 8 comply with the relationship defined in equation (2), the source energy dispersion blur generated by the electrostatic and magnetic deflection fields in a Wien filter 110 can cancel each other. Equations (2) and (3) can be used to correct for equilibrium energy dispersion.
在方程式(2)及(3)中，V p及V s係維恩過濾器區中之初級電子束及二次電子束之能量電壓，且LE係晶圓上之初級電子束之著陸能量。例如，若LE=1 kV且Vp=30 kV，則ρ=1/30，而給出θ p/θ s=0.33。因此，柱傾斜角θ p係偵測陣列角θ s的三分之一。對於具有數百個小射束之一多電子束系統，SEB角θ s可能相對較大(例如，θ s=15°)，因此傾斜柱角可為θ p=5°。 In equations (2) and (3), V p and V s are the energy voltages of the primary electron beam and the secondary electron beam in the Wien filter region, and LE is the landing energy of the primary electron beam on the wafer. For example, if LE=1 kV and Vp=30 kV, then ρ=1/30, giving θ p /θ s =0.33. Therefore, the column tilt angle θ p is one-third of the detection array angle θ s . For a multi-electron beam system with one of hundreds of beamlets, the SEB angle θ s may be relatively large (eg, θ s =15°), so the tilt cylinder angle may be θ p =5°.
方程式(2)不僅符合源能量分散之抵消條件，而且符合初級射束之對準條件。若符合對準條件，則具有圖8中之一角度θ p之傾斜初級射束被對準至物鏡109光軸。對準條件可要求維恩過濾器110之靜電場在y方向上偏轉一角度θ p且要求維恩過濾器110之磁場在-y方向上偏轉一角度2θ p。此假定圖8之橫截面係在y-z平面中。 Equation (2) not only meets the cancellation condition of the source energy dispersion, but also meets the alignment condition of the primary beam. If the alignment conditions are met, the tilted primary beam with an angle θ p in Figure 8 is aligned to the optical axis of the objective lens 109. The alignment condition may require that the electrostatic field of the Wien filter 110 be deflected by an angle θ p in the y direction and that the magnetic field of the Wien filter 110 be deflected by an angle 2θ p in the −y direction. This assumes that the cross section of Figure 8 is in the yz plane.
維恩過濾器110靜電及磁偏轉場可分別由圖3及圖4中之八極產生。歸因於偏轉場在一較大中心區(即，圖4中之等電位線)中相當均勻的事實，能量分散抵消可在一較大區中相當均勻，使得可藉由一全域維恩過濾器同時抵消圖7中之數百個小射束之能量分散模糊。The electrostatic and magnetic deflection fields of the Wien filter 110 can be generated by the eight poles in Figure 3 and Figure 4 respectively. Due to the fact that the deflection field is quite uniform in a large central area (i.e., the equipotential lines in Figure 4), the energy dispersion cancellation can be quite uniform in a large area, allowing it to be filtered by a global Wien filter The device simultaneously cancels the energy dispersion blur of hundreds of small beams in Figure 7.
若初級射束著陸能量(LE)在一範圍內改變，則與一給定(即，固定)偵測陣列111角θ s相比，二次電子束可能過偏轉或欠偏轉。然而，可運用二次電子收集光學器件(未展示)中之對準器(即，偏轉器)來校正此一未對準二次電子束。 If the primary beam landing energy (LE) varies within a range, the secondary electron beam may be over- or under-deflected compared to a given (ie, fixed) detection array 111 angle θ s . However, this misaligned secondary electron beam can be corrected using an aligner (ie, a deflector) in the secondary electron collection optics (not shown).
圖8中之維恩過濾器110之存在引入晶圓107處之小射束之像散模糊。圖8中之光學系統上之電腦模擬展示晶圓107處之像散光斑(橢圓光斑)之電子分佈在相同方向上，如圖9中所展示。即使在電子經歷磁性物鏡109之聚焦時其等之旋轉之情況下，電子仍在晶圓107處保持與其等經歷維恩過濾器110相同之方向。圖9展示中心(第0環)及第10環處分別具有0°、60°、120°、180°、240°及300°的典型小射束之七個像散模糊。The presence of Wien filter 110 in Figure 8 introduces astigmatic blurring of the beamlet at wafer 107. The computer simulation on the optical system in Figure 8 shows that the electrons in the astigmatic spot (elliptical spot) at wafer 107 are distributed in the same direction, as shown in Figure 9 . Even as the electrons rotate as they undergo focusing by the magnetic objective 109 , the electrons remain in the same direction at the wafer 107 as they experience the Wien filter 110 . Figure 9 shows seven astigmatic blurs of typical beamlets with 0°, 60°, 120°, 180°, 240° and 300° at the center (0th ring) and 10th ring respectively.
可運用一全域像散校正器來校正歸因於維恩過濾器110之存在之全部小射束之像散模糊，如圖10中所展示。可使用圖10中之八極(靜電)偏轉器之八個板作為施加兩群組電壓±Va及±Vb之兩個像散校正器。例如，在施加電壓Va=1個單位及Vb=0個單位之情況下，透過電腦模擬給出圖10中之等電位線。此實例產生在y軸方向上聚焦電子束且在x軸方向上散焦電子束之靜電場分佈。改變Va及Vb可將極角周圍之組合靜電力從0度改變為360度，使得可藉由選擇Va及Vb電壓來校正任何方向上之像散模糊。A global astigmatism corrector can be used to correct astigmatism blur for all beamlets due to the presence of Wien filter 110, as shown in Figure 10. The eight plates of the eight-pole (electrostatic) deflector in Figure 10 can be used as two astigmatism correctors applying two sets of voltages ±Va and ±Vb. For example, when the applied voltage Va=1 unit and Vb=0 unit, the equipotential lines in Figure 10 are generated through computer simulation. This example produces an electrostatic field distribution that focuses the electron beam in the y-axis direction and defocuses the electron beam in the x-axis direction. Changing Va and Vb changes the combined electrostatic force around the polar angle from 0 degrees to 360 degrees, allowing astigmatism blur in any direction to be corrected by selecting the Va and Vb voltages.
在運用圖8之全域傾斜柱及圖10之一全域像散校正器進行源能量分散及像散之校正之後，跨331個小射束之一大視域之最終光斑大小可符合所要解析度及成像均勻性，如圖11中所展示。電腦模擬進一步展示可再次由圖6中之標繪圖特性化光斑大小對射束電流關係，此意謂源能量分散及像散全部被移除而不影響最終解析度。類似於圖7及圖9，圖11中之(a)、(b)、(c)、(d)、(e)、(f)及(g)係中心(第0環)及第10環處分別具有0°、60°、120°、180°、240°及300°的小射束之最終光斑。After using the global tilt column in Figure 8 and the global astigmatism corrector in Figure 10 to correct the source energy dispersion and astigmatism, the final spot size across a large field of view of 331 small beams can meet the required resolution and Imaging uniformity, as shown in Figure 11. Computer simulations further demonstrate that spot size versus beam current can be characterized again by the plot in Figure 6, meaning that source energy dispersion and astigmatism are all removed without affecting the final resolution. Similar to Figures 7 and 9, (a), (b), (c), (d), (e), (f) and (g) in Figure 11 are the center (0th ring) and 10th ring The final light spots of the small beams are respectively 0°, 60°, 120°, 180°, 240° and 300°.
如圖12中所展示，可沿維恩過濾器110與轉移透鏡112之間之小射束之路徑增添一第二維恩過濾器127。第二維恩過濾器包含一第二靜電偏轉器128及一第二磁偏轉器129。As shown in Figure 12, a second Wien filter 127 can be added along the path of the beamlet between the Wien filter 110 and the transfer lens 112. The second Wien filter includes a second electrostatic deflector 128 and a second magnetic deflector 129 .
可使用兩個維恩過濾器來校正歸因於圖7中之一維恩過濾器之存在之源能量分散模糊。在圖12中，較接近晶圓107之下維恩過濾器110可用於將二次電子束偏轉朝向側偵測陣列111。較接近轉移透鏡112之第二(或上)維恩過濾器127可用於補償能量分散。在維恩過濾器127中產生之能量分散可用於補償在維恩過濾器110中產生之能量分散。在美國專利10,090,131中進一步描述兩個維恩過濾器之使用，該案之全文以引用的方式併入。Two Wien filters can be used to correct source energy dispersion blur due to the presence of one of the Wien filters in Figure 7. In FIG. 12 , a Wien filter 110 closer to the wafer 107 can be used to deflect the secondary electron beam toward the side detection array 111 . A second (or upper) Wien filter 127 closer to the transfer lens 112 can be used to compensate for energy dispersion. The energy dispersion produced in Wien filter 127 can be used to compensate for the energy dispersion produced in Wien filter 110 . The use of two Wien filters is further described in US Patent 10,090,131, which is incorporated by reference in its entirety.
運用圖2及圖8中之一加速磁性物鏡方案，藉由增加加速電壓Va而改良多電子小射束之解析度。加速電壓Va可增加至無電弧之一位準且使得電子小射束用磁激勵穩定地聚焦於晶圓上。Using one of the accelerating magnetic objective lens solutions in Figures 2 and 8, the resolution of multi-electron beamlets is improved by increasing the accelerating voltage Va. The accelerating voltage Va can be increased to an arc-free level and the electron beamlets are stably focused on the wafer with magnetic excitation.
使用兩個維恩過濾器來校正圖7中之源能量分散模糊，初級射束光學柱係一豎直柱，但可提供與圖8中之傾斜柱類似之一校正效能。Two Wien filters are used to correct the source energy dispersion blur in Figure 7. The primary beam optical column is a vertical column but provides a correction performance similar to the tilted column in Figure 8.
圖13係方法200之一流程圖。在201，引導複數個小射束通過在一電子束源下游之一轉移透鏡，藉此聚焦電子束。例如，可存在至少100個小射束(例如，大於300個小射束)。在202，引導小射束通過在轉移透鏡下游之一維恩過濾器，藉此將二次電子束與小射束分離。維恩過濾器可具有一靜電偏轉器及一磁偏轉器。在203，引導小射束通過一物鏡之一上極片。物鏡係在維恩過濾器下游。維恩過濾器可經組態以同時調整小射束之分散及像散。在204，引導小射束通過在上極片下游之一加速電極。加速電極可經組態以改變小射束之解析度。在205，引導小射束通過安置於物鏡之一下極片中之一電荷控制板。電荷控制板係安置於物鏡之與上極片相對之一側上。在206，引導小射束於一晶圓處。在207，在一偵測陣列處接收來自晶圓之一或多個二次電子束。Figure 13 is a flow chart of method 200. At 201, a plurality of beamlets are directed through a transfer lens downstream of an electron beam source, thereby focusing the electron beam. For example, there may be at least 100 beamlets (eg, greater than 300 beamlets). At 202, the beamlet is directed through a Wien filter downstream of the transfer lens, thereby separating the secondary electron beam from the beamlet. Wien filters can have an electrostatic deflector and a magnetic deflector. At 203, the beamlet is directed through one of the upper pole pieces of an objective lens. The objective is mounted downstream of the Wien filter. Wien filters can be configured to simultaneously adjust for beamlet dispersion and astigmatism. At 204, the beamlet is directed through one of the accelerating electrodes downstream of the upper pole piece. The accelerating electrodes can be configured to vary the resolution of the beamlets. At 205, the beamlet is directed through a charge control plate disposed in one of the lower pole pieces of the objective lens. The charge control plate is placed on the side of the objective lens opposite to the upper pole piece. At 206, the beamlet is directed at a wafer. At 207, one or more secondary electron beams from the wafer are received at a detection array.
方法200可進一步包含使用電子束源產生一電子束及將電子束轉換成複數個小射束。電子束可經引導通過一準直透鏡及安置於電子束源與轉移透鏡之間的電子束之一路徑中之一限束孔徑。Method 200 may further include generating an electron beam using an electron beam source and converting the electron beam into a plurality of beamlets. The electron beam may be directed through a collimating lens and a beam limiting aperture disposed in a path of the electron beam between the electron beam source and the transfer lens.
方法200可進一步包含運用安置於上極片上之一掃描器(即，一偏轉器)來掃描小射束。Method 200 may further include scanning the beamlet using a scanner (ie, a deflector) disposed on the upper pole piece.
方法200可進一步包含使用一孔徑陣列將一電子束分離成小射束。孔徑陣列係安置於電子束源與轉移透鏡之間之電子束之一路徑中。小射束經引導通過：一微像散校正器陣列，其安置於孔徑陣列與轉移透鏡之間之小射束之路徑中；一微偏轉器陣列，其安置於微像散校正器陣列與轉移透鏡之間之小射束之路徑中；及一微透鏡陣列，其安置於微偏轉器陣列與轉移透鏡之間之小射束之路徑中。電子束可為在孔徑陣列上游之一遠心射束。Method 200 may further include using an aperture array to split an electron beam into beamlets. The aperture array is disposed in one of the electron beam paths between the electron beam source and the transfer lens. The beamlet is directed through: a micro-astigmatism corrector array disposed in the path of the beamlet between the aperture array and the transfer lens; a micro-deflector array disposed between the micro-astigmatism corrector array and the transfer lens in the path of the beamlets between the lenses; and a microlens array disposed in the path of the beamlets between the microdeflector array and the transfer lens. The electron beam may be a telecentric beam upstream of the aperture array.
方法200可進一步包含使用維恩過濾器改變小射束之一方向，使得小射束離開維恩過濾器係按相對於其等進入維恩過濾器的定向之一角度引導。Method 200 may further include using a Wien filter to redirect a beamlet such that the beamlet exits the Wien filter at an angle relative to its orientation entering the Wien filter.
方法200可包含引導小射束通過在維恩過濾器與轉移透鏡之間的小射束之一路徑中之一第二維恩過濾器。Method 200 may include directing the beamlet through a second Wien filter in one of the beamlet's paths between the Wien filter and the transfer lens.
可按在系統之條件改變時使用方法200。例如，可在改變射束能量、著陸能量、射束電流、FOV或其他參數時使用方法200。Method 200 can be used when system conditions change. For example, method 200 may be used when changing beam energy, landing energy, beam current, FOV, or other parameters.
儘管已關於一或多項特定實施例描述本發明，然將瞭解，可在不脫離本發明之範疇之情況下製作本發明之其他實施例。因此，本發明被視為僅受限於隨附發明申請專利範圍及其合理解釋。Although the invention has been described with respect to one or more specific embodiments, it will be understood that other embodiments of the invention can be made without departing from the scope of the invention. Accordingly, the present invention is deemed to be limited only by the patentable scope of the appended invention claims and their reasonable interpretation.
100:系統 101:尖端 102:槍透鏡(GL) 103:孔徑陣列 104:微像散校正器陣列 105:微偏轉器陣列 106:微透鏡陣列(MLA) 107:晶圓(WF) 108:載物台 109:物鏡 110:維恩過濾器 111:偵測陣列 112:轉移透鏡 113:電子束 114:小射束/電子束 115:上極片 116:下極片 117:物鏡線圈 118:電荷控制板 119:加速電極 120:掃描器 121:靜電偏轉器/靜電偶極 122:磁偏轉器/磁偶極 123:極片 124:轉移透鏡線圈 125:限束孔徑(BLA) 126:準直透鏡 127:第二維恩過濾器 128:第二靜電偏轉器 129:第二磁偏轉器 200:方法 201:引導複數個小射束通過在電子束源下游之轉移透鏡，藉此聚焦電子束 202:引導小射束通過在轉移透鏡下游之維恩過濾器，藉此將二次電子束與小射束分離 203:引導小射束通過物鏡之上極片 204:引導小射束通過在上極片下游之加速電極 205:引導小射束通過安置於物鏡之下極片中之電荷控制板 206:引導小射束於晶圓處 207:在偵測陣列處接收來自晶圓之一或多個二次電子束 100:System 101: Tip 102: Gun Lens (GL) 103:Aperture array 104:Micro-astigmatism corrector array 105:Micro deflector array 106: Microlens Array (MLA) 107: Wafer (WF) 108:Carrying stage 109:Objective lens 110:Ven filter 111:Detection Array 112:Transfer lens 113:Electron beam 114:Small beam/electron beam 115: Shangji piece 116: Lower pole piece 117:Objective lens coil 118:Charge control board 119: Acceleration electrode 120:Scanner 121: Electrostatic deflector/electrostatic dipole 122:Magnetic deflector/magnetic dipole 123:pole piece 124:Transfer lens coil 125: Beam limited aperture (BLA) 126:Collimating lens 127:Second Wien filter 128: Second electrostatic deflector 129:Second magnetic deflector 200:Method 201: Guide a plurality of small beams through a transfer lens downstream of the electron beam source, thereby focusing the electron beam 202: Guide the beamlet through the Wien filter downstream of the transfer lens, thereby separating the secondary electron beam from the beamlet 203: Guide the small beam through the upper pole piece of the objective lens 204: Guide the small beam through the accelerating electrode downstream of the upper pole piece 205: Guide the small beam through the charge control plate placed in the pole piece under the objective lens 206: Guide the small beam to the wafer 207: Receive one or more secondary electron beams from the wafer at the detection array
為了更充分理解本發明之性質及目的，應參考結合隨附圖式進行之以下詳細描述，其中： 圖1係根據本發明之一系統之一實施例； 圖2係根據本發明之一成像光學器件之一實施例； 圖3係具有一個八極靜電偏轉器及八極磁偏轉器之一維恩過濾器之一實施例； 圖4繪示一個八極靜電偏轉器中之一靜電偏轉場； 圖5繪示在不存在圖1及圖2之維恩過濾器之情況下，如一晶圓之多電子光斑大小； 圖6係展示多電子束解析度隨加速電壓(Va)之改良之一曲線圖； 圖7展示歸因於一維恩過濾器之存在之源能量分散模糊； 圖8係根據本發明之校正源能量分散模糊之一全域傾斜光學柱之一實施例； 圖9展示歸因於一維恩過濾器之存在之像散模糊； 圖10繪示在一維恩過濾器中包含八極偏轉板之一全域靜電像散校正器； 圖11展示在校正能量分散及像散之後跨具有331個小射束之一大視域之影像均勻性； 圖12係根據本發明之一系統之另一實施例；及 圖13係根據本發明之一方法之一實施例之一流程圖。 For a fuller understanding of the nature and objects of the invention, reference should be made to the following detailed description taken in conjunction with the accompanying drawings, in which: Figure 1 is an embodiment of a system according to the present invention; Figure 2 is an embodiment of an imaging optical device according to the present invention; Figure 3 shows an embodiment of a Wien filter having an eight-pole electrostatic deflector and an eight-pole magnetic deflector; Figure 4 illustrates an electrostatic deflection field in an eight-pole electrostatic deflector; Figure 5 shows the multi-electron spot size of a wafer without the Wien filter of Figures 1 and 2; Figure 6 is a graph showing the improvement of multi-electron beam resolution with accelerating voltage (Va); Figure 7 shows the source of existence energy dispersion blur attributed to the one-Wien filter; Figure 8 is an embodiment of a globally tilted optical column for correcting source energy dispersion blur according to the present invention; Figure 9 shows astigmatism blur due to the presence of a 1-Wien filter; Figure 10 shows a global electrostatic astigmatism corrector including an eight-pole deflection plate in a one-Wien filter; Figure 11 shows image uniformity across a large field of view with 331 beamlets after correcting for energy dispersion and astigmatism; Figure 12 is another embodiment of a system according to the present invention; and Figure 13 is a flow chart of an embodiment of a method according to the present invention.
100:系統 100:System
101:尖端 101: Tip
102:槍透鏡(GL) 102: Gun Lens (GL)
103:孔徑陣列 103:Aperture array
104:微像散校正器陣列 104:Micro-astigmatism corrector array
105:微偏轉器陣列 105:Micro deflector array
106:微透鏡陣列(MLA) 106: Microlens Array (MLA)
107:晶圓(WF) 107: Wafer (WF)
108:載物台 108:Carrying stage
109:物鏡 109:Objective lens
110:維恩過濾器 110:Ven filter
111:偵測陣列 111:Detection Array
112:轉移透鏡 112:Transfer lens
113:電子束 113:Electron beam
114:小射束/電子束 114:Small beam/electron beam
125:限束孔徑(BLA) 125: Beam limited aperture (BLA)
126:準直透鏡 126:Collimating lens
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| WO2008101713A2 (en) * | 2007-02-22 | 2008-08-28 | Applied Materials Israel Ltd. | High throughput sem tool |
| US8362425B2 (en) * | 2011-03-23 | 2013-01-29 | Kla-Tencor Corporation | Multiple-beam system for high-speed electron-beam inspection |
| US10008360B2 (en) * | 2015-01-26 | 2018-06-26 | Hermes Microvision Inc. | Objective lens system for fast scanning large FOV |
| KR102662658B1 (en) * | 2019-03-27 | 2024-05-03 | 에이에스엠엘 네델란즈 비.브이. | System and method for alignment of secondary beam in multibeam inspection device |
| US11056312B1 (en) * | 2020-02-05 | 2021-07-06 | Kla Corporation | Micro stigmator array for multi electron beam system |
-
2022
- 2022-05-31 US US17/829,230 patent/US20240096586A1/en active Pending
-
2023
- 2023-03-08 TW TW112108419A patent/TW202405855A/en unknown
- 2023-05-17 WO PCT/US2023/022470 patent/WO2023235145A1/en unknown
Also Published As
| Publication number | Publication date |
|---|---|
| US20240096586A1 (en) | 2024-03-21 |
| WO2023235145A1 (en) | 2023-12-07 |
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